Sensor guide wire

ABSTRACT

Sensor guide wire for intravascular measurements of a physiological variable in a living body, comprising a core wire running along at least a part of the sensor guide wire and a sensor element arranged in a jacket in a sensor region of the sensor guide wire. The jacket is tubular and is provided with a jacket wall and a portion of the core wire that extends longitudinally along the sensor region forms part of the wall of the jacket, in order to provide more space in the jacket.

FIELD OF THE INVENTION

The present invention relates to a sensor guide wire for intravascularmeasurements of a physiological variable in a living body.

BACKGROUND OF THE INVENTION

In many medical procedures, various physiological conditions presentwithin a body cavity need to be monitored. These physiologicalconditions are typically physical in nature—such as pressure,temperature, rate-of-fluid flow, and provide the physician or medicaltechnician with critical information as to the status of a patient'scondition.

One device that is widely used to monitor conditions is the bloodpressure sensor. The sensor is typically included in a guide wire forintravascular measurements. A blood pressure sensor senses the magnitudeof a patient's blood pressure, and converts it into a representativeelectrical signal that is transmitted to the exterior of the patient.For most applications it is also required that the sensor iselectrically energized.

Some means of signal and energy transmission is thus required, and mostcommonly extremely thin electrical leads are provided inside the guidewire, which itself is provided in the form of a tube (having an outerdiameter of e.g. 0.35 mm), oftentimes made of stainless steel. In orderto increase the bending strength of the tubular guide wire, a core wireis positioned inside the tube. The mentioned electrical leads arepositioned in the space between the inner lumen wall and the core wire.

A large flexibility of the sensor guide is advantageous in that itallows the sensor guide to be introduced into small and tortuousvessels. It should, however, also be recognized that if the core wire istoo flexible, it would be difficult to push the sensor guide forwardinto the vessels, i.e. the sensor guide must possess a certain“pushability”. Furthermore, the sensor guide must be able to withstandthe mechanical stress exerted on the core wire especially in sharpvessel bends.

A guide wire is disclosed in EP 1 475 036, assigned to the same assigneeas the present invention, where a sensor element is positioned in ajacket in a sensor region of a distal part of the guide wire. The corewire has an enlarged section which extends through the jacket, and isprovided with a recess or depression for reception of the sensorelement.

The space within the jacket is thus very limited as it has toaccommodate both the sensor element and the core wire. The outerdiameter of the jacket is limited by the vessel geometry and the use ofother intravascular catheters to about 0.35 mm, which makes it difficultto enlarge the outer diameter of the sensor guide wire.

Prior art guide wires may also be sensitive to bending as the jacketprincipally does not bend. The parts extending from both ends of thejacket may then be exposed to stress and a risk of damage to the guidewire arises.

The object of the present invention is to achieve a sensor guide wirethat makes it possible to provide more space for sensor element(s) andaccessories than in prior art sensor guide wires. A further aim of thepresent invention is to provide a sensor guide wire that reduces therisk of bending damages to the guide wire.

SUMMARY OF THE INVENTION

The above-mentioned object is achieved by a sensor guide wire forintravascular measurements of a physiological variable in a living body,comprising: a core wire running along at least a part of the sensorguide wire; a sensor element arranged in a jacket in a sensor region ofthe sensor guide wire, wherein the jacket is tubular and is providedwith a jacket wall, wherein a portion of the core wire that extendslongitudinally along the sensor region forms part of the wall of thejacket, in order to provide more space in the jacket.

In one embodiment, the jacket wall and the portion of the core wire (7)that extends longitudinally along the sensor region, are adapted to matewith each other. Accordingly, the mating of the jacket wall and the corewire portion result in increased space in the jacket.

According to one embodiment, the jacket wall has a longitudinaldepression adapted to receive a portion of the core wire. Thus, the corewire may then be part of or even embedded in the jacket wall.

According to a further embodiment, the jacket wall has a longitudinalopening adapted to receive a portion of the core wire. Accordingly, thecore wire then constitutes the jacket wall in a part of the jacket.

Preferably, the portion of the core wire that forms part of the jacketwall is recessed and/or is compressed, in order to provide more space inthe jacket.

Advantageously, the portion of the core wire that forms part of thejacket wall is attached to the jacket by joints. Thus, a steadyattachment of the core wire to the jacket is achieved.

In one embodiment, the sensor region is arranged with centring meansadapted to place the sensor element in a central position in the jacket,in order to facilitate a correct joining of the jacket to its adjacentparts and thereby obtain a smooth envelope surface of the sensor guidewire.

Preferably, at least one end portion of the jacket or the sensingelement is provided with centring means. Accordingly, the centring meansare placed to get a satisfactory centring of the sensor element.

Advantageously, the centring means are in the shape of tabs protruding asmall distance from the inner side of the jacket or from the sensingelement, respectively, in order to control the placement of the sensingelement inside the jacket.

In one embodiment, at least one part of the core wire extendinglongitudinally along the sensor region is shaped to function as acentring means for the sensing element. Thus, part of the core wire isutilized to arrange the sensor element in a central position.

SHORT DESCRIPTION OF THE APPENDED DRAWINGS

FIG. 1 shows a sensor guide wire divided in different regions.

FIG. 2 is a longitudinal cross-section of the sensor region taken alongK-K in FIG. 1.

FIG. 3 shows the sensor region in detail.

FIG. 4 illustrates the behaviour in sharp vessel bends of a sensor guidewire with a jacket.

FIG. 5 is a cross-section of the sensor region taken along G-G in FIG.1.

FIG. 6 is a cross-section of the sensor region taken along I-I in FIG.1.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

With reference to FIG. 1, a sensor guide wire 1 for intravascularmeasurements according to the present invention is shown. The guide wireis divided in different regions, a-e, where region a is the most distalregion and e is the most proximal region. The different regions are: a)Tip region, b) Sensor region, c) Flexible region, d) Shaft region, ande) Male connector region. In an exemplary embodiment, region a) is about10-50 mm, region b) is about 1-5 mm, region c) is about 150-400 mm,region d) is about 1000-2000 mm and region e) is about 10-100 mm. Thediameter of the sensor guide wire 1 preferably varies between 0.25-2.5mm; for use in coronary arteries, the diameter is normally 0.35 mm.

The sensor region includes a tubular shaped jacket 3 (or sleeve), andthe jacket 3 accommodates a sensor element 4. In order to power thesensor element 4 and to communicate signals representing the measuredphysiological variable, one or more cables or leads for transmittingsignals are connected between the sensor element 4 and a male connector6 in the male connector region. The cables are typically routed alongthe length of the wire.

A core wire 7 is running along at least a part of the sensor guide wire1, and is preferably made from a metal, such as stainless steel, or asuperelastic metal, e.g. Nitinol®. The mechanical properties (e.g.flexibility and strength) of the sensor guide wire 1 will mainly bedetermined from the material, design and dimensions of the core wire 7.Typically a sensor guide wire 1 also includes a protecting sheath ortubing 5 encompassing the core wire 7 and the above-mentioned cables.

The core wire 7 is running lengthwise inside the jacket 3, and the corewire 7 and sensor element 4 have to adapt their sizes in dependence ofthe space inside the jacket 3 and to each other. As the outer diameterof the jacket 3 is limited to be at most around 0.35 mm, there is nopossibility to increase the outer measure of the jacket 3 to more thanthat.

The inventor of the present invention has thus realized that it ispossible to increase the inner space of the jacket 3, by letting aportion of the core wire 7 that extends longitudinally along the sensorregion form part of the wall of the jacket 3. The jacket 3 is tubularand has a transversely extending jacket wall. In one embodiment, thejacket wall and the portion of the core wire 7 are adapted to mate witheach other. The mating of the jacket wall and the core wire portionresults in increased space in the jacket, as their thickness (lateralextension) together when mating may be less than if they were separated.This is possible as they when mating may have essentially the sameeffect in respect of e.g. strength and protection capabilities as ifthey were separated. Advantageously, the jacket wall has a longitudinaldepression on its inner side adapted to receive the portion of the corewire 7. FIG. 2 shows a longitudinal cross-section of the sensor regiontaken along K-K in FIG. 1, and shows a further advantageous embodiment,wherein the jacket wall has a longitudinal opening adapted to receive aportion of the core wire 7 that extends along the jacket 3. In thiscase, a side of the core wire 7 accordingly constitutes a part of theenvelope surface of the sensor guide wire 1. The depression or openingin the jacket wall preferable extends along a major part of thelongitudinal extension of the jacket 3.

According to one embodiment, to provide more space in the jacket 3 andto fit in the above described depression and/or opening, the portion ofthe core wire 7 that forms part of the jacket wall is preferablyrecessed.

In a further embodiment, the portion of the core wire 7 that forms partof the jacket wall is compressed. Such a recess or compression can bemade by e.g. spark machining, pressing, rolling or stamping techniques.

The portion of the core wire 7 that forms part of the jacket wall isaccording to one embodiment attached to the jacket 3 by joints 8. Anexample of this embodiment is shown in FIG. 3. The joints 8 may be e.g.welded or soldered joints or other suitable joints. Another possibleattachment arrangement is some kind of adhesive, e.g. glue.

From a mechanical (i.e. bending) point of view, the jacket 3 can beregarded as stiff. A sensor guide wire 1 has to be stiff enough to bepushed forward in a narrow and tortuous vessel and yet be flexibleenough for manoeuvring in acute takeoffs. FIG. 4 is a set-upillustrating a part of a sensor guide wire 1, including a jacket 3 whichis regarded as stiff, when manoeuvred through a 90-degree bend 9. Theset-up is for illustrative purposes only, and demonstrates a situationthat the sensor guide wire 1 may encounter. The portions distally andproximally of the jacket 3 may be exposed to wear and localized stresswhen the sensor guide wire 1 is manoeuvred through the bend, if thejacket 3 is not correctly joined to its adjacent parts. In oneembodiment according to the invention, the sensor region is arrangedwith centring means adapted to place the sensor element 4 in a centralposition in the jacket 3. The centring means facilitates a correctjoining of the jacket 3 to its adjacent parts, i.e. a proximal tube 5and/or a coil 2. An essentially smooth envelope surface of the sensorguide wire 1 is then obtained, which reduces the risk of wear of theportions distally and proximally of the jacket 3.

The centring means may, according to one embodiment, be arranged at oneend portion of the jacket 3, and preferably at both ends of the jacket3. The centring means may be in the shape of tabs 10 protruding a smalldistance from the inner side of the jacket 3. FIG. 5 is a cross-sectionof the sensor region taken along G-G in FIG. 1, which shows the centringmeans arranged as tabs 10 with a symmetric spacing on the inner side ofa distal part of the jacket 3. FIG. 6 is a cross-section of the sensorregion taken along I-I in FIG. 1, which shows protruding tabs 10 in aproximal part of the jacket 3. The tabs 10 are here positioned oppositeeach other on the inner side of the jacket 3. FIG. 6 also shows anembodiment where the shape of the core wire 7 is utilized as a centringmeans, i.e. at least one part of the core wire 7 extendinglongitudinally along the sensor region is shaped to function as acentring means for the sensor element 4. Other spacings and positionsthan the ones exemplified are of course possible. It is to be understoodthat it is possible to arrange the tabs 10 on the sensing elementinstead of on the inner side of the jacket 3, in a corresponding way asexplained above.

The present invention is not limited to the above-described preferredembodiments. Various alternatives, modifications and equivalents may beused. Therefore, the above embodiments should not be taken as limitingthe scope of the invention, which is defined by the appending claims.

1. Sensor guide wire for intravascular measurements of a physiologicalvariable in a living body, comprising: a core wire running along atleast a part of said sensor guide wire; a sensor element arranged in ajacket in a sensor region of said sensor guide wire, wherein said jacketis tubular and is provided with a jacket wall; characterized in that aportion of the core wire that extends longitudinally along the sensorregion forms part of the wall of said jacket, in order to provide morespace in said jacket.
 2. Sensor guide wire according to claim 1, whereinsaid jacket wall and said portion of the core wire are adapted to matewith each other.
 3. Sensor guide wire according to claim 1, wherein saidjacket wall has a longitudinal depression adapted to receive saidportion of said core wire.
 4. Sensor guide wire according to claim 1,wherein said jacket wall has a longitudinal opening adapted to receivesaid portion of said core wire.
 5. Sensor guide wire according to claim1, wherein said portion of the core wire that forms part of said jacketwall, is recessed.
 6. Sensor guide wire according to claim 1, whereinsaid portion of the core wire that forms part of said jacket wall, iscompressed.
 7. Sensor guide wire according to claim 1, wherein saidportion of the core wire that forms part of said jacket wall, isattached to said jacket by joints.
 8. Sensor guide wire according toclaim 1, wherein said sensor region is arranged with centring meansadapted to place said sensor element in a central position in saidjacket, in order to obtain a smooth envelope surface of said sensorguide wire.
 9. Sensor guide wire according to claim 8, wherein at leastone end portion of said jacket or said sensing element is provided withcentring means.
 10. Sensor guide wire according to claim 9, wherein saidcentring means are in the shape of tabs protruding a small distance fromthe inner side of said jacket or from said sensing element,respectively.
 11. Sensor guide wire according to claim 8, wherein atleast one part of said core wire extending longitudinally along saidsensor region is shaped to function as a centring means said sensorelement.